The deeper meaning of this threefold rhythm will become clear when we consider it against the background of what we observed in the metamorphosis of the leaf. Take the mallow leaf; its metamorphosis shows a step-wise progression from coarser to finer forms, whereby the characteristic plan of the leaf comes more and more into view, so that in the topmost leaf it reaches a certain stage of perfection. Now we observe that in the calyx this stage is not improved on, but that the plant recurs to a much simpler formation.